The adjustment of the audio level in many electronic devices, which are capable of producing audio, such as a portable two-way radio, is achieved by rotating a knob. Generally, the knob is engaged to a rotating shaft of a potentiometer, and rotating the knob increases or decreases the audio power delivered to a speaker. The amount of control one has in setting a desired audio level is proportional to the rotational torque required to rotate the shaft. A lower rotational torque provides less control, while a higher rotational torque provides more control over audio adjustments. A low rotational torque may cause problems in maintaining the desired audio setting, and may easily cause inadvertent rotation of the knob. Therefore, it is desirable to increase the rotational torque of a rotational control assembly.
One approach to increase the rotational torque comprises incorporating a means to increase the rotational torque of the potentiometer itself. This approach, however, is costly, and reduces the life cycle of the potentiometer. Another approach, which is particularly used in two-way portable radio's manufactured by Motorola Inc., comprises inserting a friction causing element, such as a rubber washer, between the bottom surface of the knob and the escutcheon of the radio. This approach causes difficulty in assembly, and large variations in the process. This is because downward pressure must be exerted on the knob, and a set screw must be tightened to adjust the rotational torque of each radio individually.